Installing Docker & First Containers

Now that you understand what containers are, it is time to install Docker and run your first containers. This lesson covers installation on all major platforms, essential commands for pulling images and managing containers, and how to inspect and debug running containers.

---

Installing Docker

Linux (Ubuntu/Debian)

# Remove old versions
sudo apt-get remove docker docker-engine docker.io containerd runc

# Install prerequisites
sudo apt-get update
sudo apt-get install -y ca-certificates curl gnupg

# Add Docker's official GPG key
sudo install -m 0755 -d /etc/apt/keyrings
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | \
  sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg

# Add the repository
echo \
  "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] \
  https://download.docker.com/linux/ubuntu \
  $(. /etc/os-release && echo \$VERSION_CODENAME) stable" | \
  sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

# Install Docker Engine
sudo apt-get update
sudo apt-get install -y docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin

# Add your user to the docker group (avoids needing sudo)
sudo usermod -aG docker \$USER
# Log out and back in for group change to take effect

macOS

1. Download Docker Desktop from docker.com/products/docker-desktop
2. Open the .dmg file and drag Docker to Applications
3. Launch Docker Desktop — it runs a lightweight Linux VM under the hood

Windows

1. Enable WSL 2 (Windows Subsystem for Linux)
2. Download Docker Desktop from the Docker website
3. During installation, ensure "Use WSL 2 instead of Hyper-V" is selected
4. Restart your computer when prompted

Verify Installation

docker --version
# Docker version 27.x.x, build xxxxxxx

docker info
# Shows daemon info, storage driver, runtime, etc.

---

Your First Container: Hello World

docker run hello-world

What happens behind the scenes:

1. Docker checks for the hello-world image locally
2. If not found, it pulls the image from Docker Hub
3. Docker creates a container from the image
4. The container runs, prints a message, and exits

---

Pulling Images

You do not need to run a container to download an image. Use docker pull:

# Pull the latest nginx image
docker pull nginx

# Pull a specific version
docker pull nginx:1.25-alpine

# Pull from a different registry
docker pull ghcr.io/owner/image:tag

Listing Local Images

docker images
# REPOSITORY   TAG            IMAGE ID       CREATED        SIZE
# nginx        latest         a8758716bb6a   2 weeks ago    187MB
# nginx        1.25-alpine    1e6fd4d1c8b7   3 weeks ago    41MB

---

Running Containers

The docker run command is the most commonly used Docker command. It creates and starts a container in one step.

Basic Syntax

docker run [OPTIONS] IMAGE [COMMAND] [ARG...]

Common Options

Flag	Purpose
-d	Run in detached (background) mode
-it	Interactive mode with a terminal (TTY)
--name NAME	Assign a name to the container
-p HOST:CONTAINER	Map a host port to a container port
-e KEY=VALUE	Set an environment variable
--rm	Automatically remove the container when it exits
-v HOST:CONTAINER	Mount a volume or bind mount

Examples

# Run nginx in the background, mapping port 8080 to 80
docker run -d --name my-nginx -p 8080:80 nginx

# Run an interactive Ubuntu shell
docker run -it --rm ubuntu bash

# Run with an environment variable
docker run -d --name my-db -e POSTGRES_PASSWORD=secret postgres:16

---

Container Lifecycle Commands

Listing Containers